Such apparatus constituted by a fluorescent electric tube emitting radiations in the ultra-violet, of a very precise wave-length, are known to be used in particular in sensitive environments at risk, such as medical or hospital premises, rooms for preservation, working or packing food products, etc.
The ultra-violet radiations of the known wave-length (2537 Angstroms) are used for their specifically germicidal and bacteriostatic properties.
To that end, boxes containing the radiation emitter tubes are used (avoiding these radiations attaining the staff's sight), the air being capable of being placed in natural or forced circulation around the tubes so as to provoke, as such circulation continues, the destruction of the germs present on the micro-dust in suspension in the air.
It is also known that such U.V. radiation generator tubes are subjected to ageing when their radiation intensity and flowrate drop, in the same way as, further to deposits, dirt or dust, they may lose a large part of their efficiency.
As these tubes emit, parallel to the ultra-violet radiations, radiations in the visible light, particularly blue, it is not possible to detect, a priori and simply by looking, the state of functioning or the degree of efficiency of the radiation, since only the blue light visible to the eye may be detected and this light, totally inefficient and without germicidal properties per se, is in no way a sign of the existence and magnitude of the parallel ultra-violet emissions.
Consequently, the U.V. tube frequently remains in place, continuing to emit its bluish light, whilst it has become totally inefficient without any germicidal action.
In the present state of the art, in order to detect the state of non-functioning of an U.V. tube further to ageing thereof or to deposit of dirt forming a screen, these tubes must be subjected to periodic maintenance in the form of an individual examination to check, during this systematic operation, the apparatus having to be replaced, renovated or maintained.
Consequently, the efficient maintenance of these apparatus depends on the staff's vigilance and any shortcoming in this respect leads to consequences which may be fatal for the patients, if only because, between two spot checks, one or more tubes may have become totally inefficient, which inefficiency will possibly be detected only at the subsequent control, consequently leaving a period of time during which the air is not protected.
In addition, verification is effected by using a portable dosimeter which requires opening the housing of the apparatus, the U.V. tubes necessarily being in action at that moment; the dosimeter is exposed to the field of the radiations emitted by the tube for a determined time, period during which the service staff therefore remains exposed to the U.V. radiations; such working conditions are not satisfactory as they are dangerous for the operator's sight and face; for these reasons, hospital staff have no great incentive to carry out such periodic verifications.
There is therefore a need for a method and apparatus making it possible to avoid, on the one hand, leaving an apparatus apparently in operation whilst it is in fact inactive, and, on the other hand, exposing the service staff to the U.V. radiations when making the verifications.
It is precisely an object of the invention to respond to this need and to overcome the drawbacks and shortcomings of the prior art as set forth hereinbefore.